/Engine/Source/Editor/UnrealEd/Public/Subsystems/EditorActorSubsystem.h
Find all loaded Actors in the world editor. Exclude actor that are pending kill, in PIE, PreviewEditor, ...
List of found Actors
[TArray](API\Runtime\Core\Containers\TArray)< class [AActor](API\Runtime\Engine\GameFramework\AActor) * > GetAllLevelActors()